1. Field of the Invention
The present invention relates to a semiconducting silicon device, and particularly pertains to a layer electrode therefore which avoids electrode-related deteriorations in using such silicon devices at high temperatures.
2. Description of the Prior Art
Heretofore, as a way of preventing the deterioration of multi-layer electrodes at high temperatures, various methods of protecting silicon devices have been contemplated, including packaging, etc.
Where it is impracticable because of some operational limitations to apply adequate protective measures such as packaging on silicon devices, satisfactory results can be obtained only infrequently with conventional multilayer electrode. For example, a thermal head having a heating layer provided in part of the semiconductor silicon is available. The thermal head is in the stage of practical application in various fields, providing a recording system simplified in structure and operation.
The thermal degradation of the thermal head in equipment featuring maintenance-free operation poses a major factor govering the guarantee period of such equipment. In the thermal head having the heating layer in part of the semiconductor silicon above-mentioned, the thermal deterioration is more pronounced at the electrode part than at the heating part. That is to say, at the area where the heating part and the electrode part make contact with one another (the so-called contact part), or due to the thermal degradation of the electrode material, the recording quality is lowered.
A means to solve this problem may be found in the electrode structures for use at high temperatures which have been developed by conventional IC techniques [for instance, L. E. Terry & R. W. Wilson; Proc. IEEE, Vol 57, No. 9, P. 1580 (1969)]. These electrode structures developed by IC techniques involve very complex multi-layer structures, are highly costly, and their applications to thermal heads without modifications have not brought about satisfactory results. Thus, as electrodes for the thermal heads of this kind, aluminum(Al) which is capable of making proper Ohmic contact, and shows excellent serviceability, etc., has hitherto been most often used. However, aluminum is susceptible to corrosion, and moreover, direct soldering on aluminum is usually difficult. As an electrode in which these two disadvantages are removed, for example, Cu-Ni may be contemplated. In this instance, nickel (Ni) has a much larger coefficient of thermal expansion than that of silicon, and also has a large Young's modulus, and accordingly, if the nickel layer is made thick (2.about.3.mu.)in order to prevent the thermal diffusion of the solder layer into the silicon, the resultant large shearing stress imposed on the surface of the silicon element, as its temperature rises, will cause deterioration of the element.
An electrode material which is highly unsusceptible to environmental influences and because of the structural difficulty in perfectly packaging the electrode material would raise a problem that by the force imposed by the heat at the time of recording, the electrode part might be stripped from the semiconductor silicon and the holding part therefor on which it is adhesively placed.